Combustion apparatus provided with a flame-holding assembly



Oct. 23, 1951 H. L. HADESTAD 2,572,723

coMBusTloN APPARATUS PROVIDED WITH A FLAME-HOLDING ASSEMBLY Filed April18, 195o ATTORNEY Patented Oct. 23, 1951 )OMBUSTION APPARATUS PROVIDEDWITH A FLAMEfI-IOLDING ASSEMBLY lHarold L. Hildestad, Swarthmore, Pa.,assigner to Westinghouse Electric Corporation, East Pittsburgh, Pa., acorporation of Pennsylvania Application April 18, 1950, Serial No.156,557

4 Claims.

This invention relates to power plants, and more particularly to anaviation power plant of the jet propulsion class.

To augment the available thrust output oi an aviation jet propulsionpower plant, such as a turbojet engine, it has been proposed to provideafterburner` apparatus adapted for combustion of additional fuel in thestream of gases 'flowing from the turbine. The velocity of turbineexhaust gases flowing through such an afterburner is normally greaterthan iifty feet per second, tending to exceed that of the flame ofcombustion of the afterburner fuel, and is vpreferably controlled' byimposition of a flame-heider vin the gas stream, so that sufficientlocal stagnation can be produced to ensure Ythat the flame will bemaintained in thedesired combustion region of the power plant. 1t is aprincipal object of the present invention to provide an improvedname-holder device of this type.

With a stationary flame-holder, `the large projected area of the elementrelative to the gas flow area tends to effect unnecessary pressure dropand consequent thrust loss during nonafterburning operation of the powerplant. Furthermore, operation of the afterburner to effect partialthrust augmentation is difficult, when 4a nonadjustable flame-holder isemployed. YIt is another object of the present invention to provide aretractible flame-holder assembly serving -to obviate the foregoingdiiculties.

A further object is the provision of -an improved flame-holder assemblyfor a turbojet power plant, including retractiblefelements mov-A able inincrements or steps through a yrange of operative positions for Varying`the .available thrust augmentation characteristics'thereof, and havinga fully retracted position in which thrust loss due .to pressure dropinduced by the name-J holder Ais reduced to zero, when it is desired tooperate the Aturbojet power plant without after-A burning.

Theseand other objects are effected by the invention as will be apparentfrom the following description and claims taken in connection with theaccompanying drawing, forming a part of this application, in which: Y

Fig. 1 is a diagrammatic elevational View, partly in section,l of atypical turbojet power plant equipped with `an afterburner and animproved flame-holder device constructed in accordance with theinvention;

Fig. 2 is an enlarged detail, sectional view of the name-holder andrelated portions of the afterburner shown in Fig. 1; and

Fig. 3 is a sectional view, in enlarged detail, of a portion of theflame-holderl apparatus, taken along the line III- III of Fig. 2.

The power plant shown schematically in Fig. 1 includes a gas turbineengine I@ and an afterburner apparatus II, which -are adapted to bemounted in the fuselage or wing of an aircraft (not shown). The gasturbine engine itv comprises a generally cylindrical casing structure I2having mounted along the axis thereof an inner sectional core structureI3, the annular space formed between the two structures constituting auid iiow passageway i4 which extends through the engine envelope from aforwardly directed air inlet opening I5 to a turbine exhaustcommunication I6. The operating elements of the engine are mounted inaxial alignment within the casing structure I2, in order to minimizeYthe frontal dimensions oi the engine and consequent drag thereof duringflight of the aircraft. These elements comprise an axial-flow compressorI8, annular combustion apparatus I9 anda turbine 20, the rotor of whichis operatively connected to the rotor of the compressor I8 by a shaft 2Ihaving suitable journaled support in the casing structure. y

The afterburner apparatus II comprises a cylindrical casing structure24, the forward end of which is suitably fitted to the complementaryturbine discharge end of the engine casing structure I2, so that theinterior spaceor combustion chamber 25 of the aiterburner apparatus`com-.- municates with' the turbine discharge passage I6. Theafterburner combustion 'chamber 2.5 extends axially through the casingstructure 24 to a rearwardly disposed exhaust nozzle 26, which may beequipped with suitable variable ow confV trolling mechanism 2l. Mountedwithin the combustion chamber 25 are a plurality of :fuel supply nozzlesand manifolds 28, which are adapted to be connected to a suitableafter.v burner fuel control system (not shown). The manifolds 28 may besupported by radially glis-` posed strutsrZil extending from the casingstruc-A ture 24. An axially arranged tubular fairing 30,

also carried `on the struts 29, is coaxially disposed in the chamber 25and extends from a plane downstream of the turbine 28 to a pointintermediate the manifolds 28 and the nozzle 26. The downstream end ofthe fairing 36 carries a flame-holder assembly 3|, which is ccnstructedin accordance with the invention as hereinafter more fully explained.

In operation of the power plant, air entering the inlet opening |5 iscompressed by the compressor I8 and delivered to the annular combustionapparatus |9 for supporting combustion of fuel that is supplied theretothrough the medium of suitable nozzles (not shown). The resultant hotmotive fluid issuing from the combustion apparatus |9 is then expandedthrough the turbine 20 and exhausted into the combustion chamber 25 ofthe afterburner apparatus Where additional fuel directed from themanifolds 28 toward the flame-holder device 3|, hereinafter described,may be burned when it is desired to augment the thrust energy of thegases finally discharged through the nozzle 26.

According to the invention, the flame-holder device 3| is mounted in thecombustion chamber 25 of the afterburner apparatus at a positiondownstream of the manifolds 28 but well in advance of the nozzle 26, asshown in Fig. 1. Referring to Fig. 2, the name-holder assembly 3|comprises a screw-threaded rotary shaft 35 mounted coaxially within thefairing 30, the opposite ends of the shaft being journaled in suitablebearings 36 and 31, and a plurality of radially disposed arms 38, theinner ends of which are pivotally connected by pins 39 to radial lugportions of a nut element 40 having a threaded .bore and movably engagedon the shaft 35. The nut element 40 is movable along the rotary shaft 40from the rear position illustrated to a forward position as shown indotted lines in Fig. 2. The radial arms 38 extend outwardly throughcorrespondingly spaced longitudinal slots 4| formed in the fairing 30,and are adapted to ride over rounded downstream end walls 42 of therespective slots when the ends connected to the nut element 48 are movedrearwardly therewith, or toward the right as viewed in Fig. 2. Duringtraverse of the nut element 40 to its forward position, the arms 38 aredrawn against the upstream edges of the slots 4| and are therebygradually retracted into the fairing 30, until movement to the fullyretracted position, as shown in dotted lines. It will be apparent thatthe several arms 38 are thus adapted to be readily removed and renewedin case it becomes necessary to effect repairs following extendedoperation of the afterburner.

Suitable gearing may be provided for eiecting selective rotation of theshaft 35, such as a bevel gear 45 secured to the forward end thereof,and a laterally disposed shaft 46 having a bevel gear 41 meshed with therst gear and adapted to be operated by conventional actuator motoi`means (not shown), which may be mounted externally of the power plant.The shaft 46 is contained within one of the struts 29 and is adapted tobe journaled on bearings 48 and 49 carried on the fairing 30 and outercasing 24, respectively.

From the foregoing, it will thus be seen that a retractible flame-holderdevice constructed in accordance with the invention may be variouslypositioned to present suicient drag or surface area to effect properretention of a combustion flame for augmenting thrust to any desired4degree in a conventional afterburner apparatus. Undernon-afterburningconditions, or when the power plant is operated only on the thrust of thturbine exhaust, the flame-holder assembly may be retracted to reducepressure loss to zero. The relatively loosely connected elements of theimproved iiame-holder assemblage are adapted to expand and contractindependently, to avoid undue stressing upon sudden changes in thermalcharacteristics. With the flame-holder device supported through themedium of pins having limited contact only with the central fairingstructure, local supports that might effect transfer of heat to theouter casing structure are 'eliminated. In addition, the separateelements of the assembly are individually replaceable in the event offailure of any part in service, without necessitating the discarding ofother elements in good condition.

While the invention has been shown in but one form, it will be obviousto those skilled in the art that it is not so limited, but issusceptible of various changes and modifications without departing fromthe spirit thereof.

What is claimed is:

1. In combustion apparatus for a power plant, casing structure forming acombustion chamber through which rburning fuel and hot motive gases arepropelled at high velocity, a retractible flameholder assembly normallyinterposed in said chamber for creating a degree of stagnancy in the gasstream sufficient to effect retention of a flame formation within thecombustion cham.'- ber, said flame-holder assembly comprising aplurality of radially arranged retractible members, and meansoperatively connected to the inner ends of said members for effectingVoutward or inward movement thereof relative to said chamber.

2. In combustion apparatus for a power plant, casing structure forming acombustion chamber through which burning fuel and hot motive gases arepropelled at high velocity, a retractible flameholder assembly normallyinterposed in said chamber for creating a degree of stagnancy in the gasstream sucient to eifect retention of'a ame formation within thecombustion chamber, said flame-holder assembly comprising a plu'- ralityof radially arranged retractible members, an actuating memberoperatively connected to said retractible members, and means foreffecting travel of said operating member along the axis of said powerplant from a position in which said retractible members are fullyprojected into said chamber to a position in which said retractiblemembers are substantially withdrawn from said chamber.

3. In combustion apparatus for a power plant, casing structure forming acombustion chamber through which burning fuel and hot motive gases arepropelled at high velocity, a retractible flameholder assemblyinterposed in saidV chamber for creating a degree of stagnancy in thegas stream sufficient to eiect retention of a flame formation within thecombustion chamber, said flameholder assembly comprising a centralfairing structure, a longitudinally shiftable element mounted therein, apluralityof radially disposed arms having inner ends connected tosaidelee.

ment and slidably engaging said fairingstru'cture, said arms beingfreely .extendable from a retracted position within said fairingStructure to an outer position within said chamber in a plane normalrelative to the axis of said casing.

4. In combustion apparatus for a power plant, casing structure having anapertured central fairing and forming an annular combustion' 5 chamberIthrough which burning fuel and hot motive gases are propelled at highvelocity, a retractible flame-holder assembly supported on said fairingand adapted to be interposed in the stream of gases for creating adegree of stag'afncy suillcient to effect retention of a flame formationwithin the combustion chamber, said flame-holder assembly comprising aplurality of spaced radially arranged arm elements having outer portions'extending into said combustion chamber and inner ends slidably engagedin the apertures of said fairing, actuating means including an Waxiallydisposed rotary threaded shaft journaled in said fairing, and a nutengaged on said 'shaft and pivotally connected to said inner ends of the15 2,503,006

arm elements, whereby said arm elements of the llame-holder assembly arerendered relatively movable outwardly into said chamber or inwardlytoward a retracted position within said fairing for varying theflame-holding characteristics of said assembly.

HAROLD L. I-IILDESTAD.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Name Date Stalker Apr. 4, 1950 Number

